Mechanism of immunity against micro-organisms 193 



The bactericidal substance, then, is essentially some substance 

 which remains inside the uninjured phagocytes in the living animal 

 but which escapes from these cells when they are injured, either in 

 the body of the animal or outside in the blood withdrawn from the 

 organism. Buclmer has given to this substance the name of alexine 

 and we must now determine whether this substance is the same 

 cytase which digests the formed elements on their resorption. 



Since his first researches on the power of one normal blood serum [204] 

 to dissolve the red corpuscles of another species, Buchner 1 has main- 

 tained the identity of the haemolytic substance with the bactericidal 

 substance of the same serum. In both cases we have to do, according 

 to him, with one and the same substance of an albuminoid nature, 

 with the same "alexine." In his later work, Buchner attempted 

 to confirm and develop this thesis. Bordet 2 has, on several occa- 

 sions, brought forward arguments in favour of the same view ; but 

 against this Ehrlich and Morgenroth 3 have declared themselves. Ac- 

 cording to these observers a single serum may contain several 

 alexines or "complements." The same serum may even contain 

 two complements, one of which is destroyed by heating to 55 C., 

 whilst the other, much more stable as to the action of heat, resists 

 this temperature. In one of their most recent memoirs, Ehrlich 



as a rule, much more feeble than the action of serums and exudations and is not 

 modified by heating to 55 56 C. In certain aqueous humours, a little cytase, 

 or true bactericidal substance, may come into play, for we find aqueous humours 

 which coagulate and which, when centrifugalised, show a small deposit of leucocytes. 

 These results have been obtained by Mme. Metchnikoff. 



It must not be forgotten also that, even in the bactericidal action of blood 

 serums, a certain factor is the change of medium which the micro-organisms ex- 

 perience with the plasmolytic phenomena which follow. But it is not possible to 

 ascribe to this factor the whole of the bactericidal property of serums and exudations, 

 as is done by Baumgarten (Arb. a. d. pathol.-anat. Inst. zu Tubingen, 1899, Bd. in, 

 S. 1, and Berl. klin. IVchnschr., 1900, SS. 136, 162, 192), and his pupils Jetter and Walz 

 supported by A. Fischer (Ztschr.f. Hyg., Leipzig, 1900, Bd. xxxv, S. 1). The idea of 

 reducing the destruction of bacteria in serums and exudations to the effect of osmotic 

 pressure has been recently elaborately analysed by v. Lingelsheim (Ztschr. f. Hyg., 

 Leipzig, 1901, Bd. xxxvn, S. 131). With great justness he comes to the conclusion that 

 " the existence in extravascular blood or in serum, of bactericidal substances acting 

 as soluble ferments can now no longer be denied " (p. 167). In studying this question 

 we must not lose sight of the fact that these bactericidal substances (alexines, 

 complements, or cytases) give rise to the production in the animal organism of 

 antagonistic substances as described by us in the 5th Chapter. 



1 Verhandl. d. Congresses/, inn. Med., Wiesbaden, 1892, S. 273. 



2 Ann. de VInst. Pasteur, Paris, 1900, t. xiv, p. 257 ; 1901, t xv, p. 312. 



3 Berl klin. Wchnschr., 1900, SS. 453, 677. 



B. 13 



